How to complete the second Outbreak main quest Easter egg in Call of Duty: Black Ops Cold War Zombies

gamepur.com:

Shortly following the addition of the first Easter egg main quest in Outbreak on Call of Duty: Black Ops Cold War, developer Treyarch announced that the new giant Zombies experience would receive an additional quest in Season 4. The studio lived up to its promise by delivering one of the most straightforward and quickest Easter eggs ever released in Zombies. Here is how to complete the second Easter egg main quest in Outbreak in Call of Duty: Black Ops Cold War Zombies.

To be quite frank, there is not much to this Easter egg quest compared to past ones in the series. There is never a moment that requires you to use a specific weapon or item, so set up your loadout with whatever you feel most comfortable with. The closest thing to a boss fight at the end is comparable to an Orda side objective from a typical Outbreak game.

The first step involves reaching round three. While doing this, be sure to complete all side objectives and explore the map thoroughly for resources to make you stronger. If you feel brave enough, you can skip round two by shooting the beacon at the end of the first round as it is powering up to teleport you.

When you get to round three, there will be a red portal hidden somewhere on the map you arrived on unless it is Sanatorium. If you did get warped to Sanatorium, you will need to play through the round and warp to another area to proceed with this quest.

On each map, there is one portal location.